Direct contacts between fibers from the ventrolateral thalamic nucleus and frontal cortical neurons projecting to the striatum: a light-microscopy study in the rat.
The aim of the present study was to improve our knowledge of the synaptic organization of one major motor loop, the thalamo-fronto-striate system. We examined, within the motor and sensorimotor (Fr1-3, FL, HL) cortices, the organization of the synaptic articulation between thalamic terminals and fronto-striatal neurons. An anterograde tracer (Phaseolus vulgaris leuco-agglutinin) was used to label the fibers from the ventrolateral (VL) thalamic nucleus and a retrograde tracer (subunit b of the cholera toxin) was employed to label the neurons of the frontal cortex projecting to the dorso-lateral quadrant of the caudate-putamen. Our findings indicated that anterogradely labeled fibers arising from the VL formed appositions, presumably synaptic contacts, with retrogradely labeled corticostriate neurons within layer V and, to a lesser degree, within layer III of the frontal cortex. These direct contacts were axo-somatic or axo-dendritic. These findings suggest that some aspects of the motor control mediated by the thalamo-fronto-striate loop could be partly achieved by monosynaptic circuits.
Zin-Ka-Ieu
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S
CNRS UMR 6558, Département des Neurosciences, Université de Poitiers, France.
Roger
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M
Arnault
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P
D000818:Animals; D001931:Brain Mapping; D002772:Cholera Toxin; D003342:Corpus Striatum / Q000502:physiology*; D005260:Female; D005625:Frontal Lobe / Q000166:cytology / Q000502:physiology*; D008297:Male; D009412:Nerve Fibers / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D010835:Phytohemagglutinins; D051381:Rats; D017208:Rats, Wistar; D009435:Synaptic Transmission / Q000502:physiology*; D013787:Thalamic Nuclei / Q000502:physiology*
D010835:Phytohemagglutinins; C100156:leukoagglutinins, plants; D002772:Cholera Toxin